In recent years, in the field of endoscope apparatuses, a variety of endoscopes have been developed, such as a laser scanning endoscope that drives the tip of a scope by vibration in a body cavity, irradiates laser light onto an examination site while scanning, detects the resulting reflected light and the like, and generates a 2D image; a confocal endoscope that obtains a clear, high-magnification and high-resolution image using a confocal technique; and an endoscope equipped with a laser light source used to generate white light with a fluorescent body and irradiate an examination site. In such apparatuses, the resolution depends on the spot diameter of the irradiation light. Therefore, in order to obtain high resolution, it is necessary to convey light from a laser light source using a single-mode optical fiber, rather than with a lamp light source and light guide bundle of an imager endoscope. Hence, the single-mode optical fiber needs to be repeatedly attached and detached between the housing and scope.
As connection methods for attachment and detachment of a single-mode optical fiber, standards such as FC, SC, ST, MU, and LC have been established in the field of optical communication (for example, see NPL 1 to NPL 3). These connection methods are for using an optical adapter with a split sleeve to connect optical fiber connectors that each have a ferrule in which the tip of an optical fiber is embedded. The ferrule is a cylindrical member produced to be coaxial with the fiber that passes through the center thereof in order to connect two optical fibers. The split sleeve is a cylindrical member for aligning ferrules in series and abutting them together and has a slit in the longitudinal direction. In this method, the ferrules of the contacting optical fiber connectors are each inserted into the split sleeve from the sides of the optical fiber adapter, and the cores of the optical fibers are abutted and aligned inside the split sleeve. The split sleeve is formed from a hard material, such as zirconia, and serves to position and hold the ferrules together. In these standard connection methods, in order to ensure that the pair of ferrules are abutted against each other, a spring is provided in the housing of each connector to push the ferrule towards the connecting direction of the connector.